Portable Optical Ablation System

ABSTRACT

The present invention includes an apparatus and method of surgical ablative material removal “in-vivo” or from an outside surface with a short optical pulse that is amplified and compressed using either an optically-pumped-amplifier and air-path between gratings compressor combination or a SOA and chirped fiber compressor combination, wherein the generating, amplifying and compressing are done within a portable system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation application of U.S. patentapplication Ser. No. 11/894,867 filed Aug. 21, 2007, and titled“Portable Optical Ablation System”, which is a continuation applicationof U.S. patent application Ser. No. 10/916,017 filed Aug. 11, 2004 andtitled “Man-Portable Optical Ablation System” which is acontinuation-in-part of Patent Application Serial No. PCT/US2004/015913filed on May 19, 2004 and titled “Trains of Ablation Pulses fromMultiple Optical Amplifiers” which claims the benefit of U.S.Provisional Patent Application Ser. No. 60/471,971 filed on May 20, 2003and titled “Stretched Optical Pulse Amplification and Compression,” U.S.Provisional Patent Application Ser. No. 60/471,922 filed on May 20, 2003and titled “Laser Machining,” and U.S. Provisional Patent ApplicationSer. No. 60/503,578 filed on Sep. 17, 2003 and titled “ControllingOptically-Pumped Optical Pulse Amplifiers;” this application also claimsthe benefit of U.S. Provisional Patent Application Ser. No. 60/494,321filed on Aug. 11, 2003 and titled “Man-Portable Optical AblationSystem.” The disclosures of the aforementioned patent and patentapplications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates in general to the field of lightamplification and, more particularly to the altering the emission of anablation beam for safety or control.

2. Description of Related Art

Ablative material removal is especially useful for medical purposes,either in-vivo or on the outside surface (e.g., skin or tooth), as it isessentially non-thermal and generally painless. Ablative removal ofmaterial is generally done with a short optical pulse that is stretched,amplified and then compressed. A number of types of laser amplifiershave been used for the amplification, including fiber-amplifiers. Fiberamplifiers have a storage lifetime of about 100 to 300 microseconds.While some measurements have been made at higher repetition rates, thesemeasurements have shown an approximately linear decrease in pulseenergy, and for ablations purposes, fiber amplifiers have been operatedwith a time between pulses of equal to or greater than the storagelifetime, and, thus, are generally run a rep rate of less than 3-10 kHz.

Laser machining can remove ablatively material by disassociate thesurface atoms and melting the material. Laser ablation is doneefficiently with a beam of short pulses (generally a pulse-duration ofthree picoseconds or less). Techniques for generating these ultra-shortpulses (USP) are described, e.g., in a book entitled “Femtosecond LaserPulses” (C. Rulliere, editor), published 1998, Springer-Verlag BerlinHeidelberg N.Y. Generally large systems, such as Ti:Sapphire, are usedfor generating ultra-short pulses (USP).

USP phenomenon was first observed in the 1970's, when it was discoveredthat mode-locking a broad-spectrum laser could produce ultra-shortpulses. The minimum pulse duration attainable is limited by thebandwidth of the gain medium, which is inversely proportional to thisminimal or Fourier-transform-limited pulse duration. Mode-locked pulsesare typically very short and will spread (i.e., undergo temporaldispersion) as they traverse any medium. Subsequent pulse-compressiontechniques are often used to obtain USP's. Pulse dispersion can occurwithin the laser cavity so that compression techniques are sometimesadded intra-cavity. When high-power pulses are desired, they areintentionally lengthened before amplification to avoid internalcomponent optical damage. This is referred to as “Chirped PulseAmplification” (CPA). The pulse is subsequently compressed to obtain ahigh peak power (pulse-energy amplification and pulse-durationcompression).

SUMMARY OF THE INVENTION

Ablative material removal with a short optical pulse is especiallyuseful for medical purposes and can be done either in-vivo or on thebody surface, as it is essentially non-thermal and generally painless.Previously, ablative systems include optical benches weighing perhaps1,000 pounds and occupying about 300 cubic feet. One embodiment of thepresent invention includes a system that weighs 100 pounds or less andoccupies 2.5 cubic feet or less.

One embodiment of the present invention includes an amplifier and apulse-compressor, enabling the invention to be man-portable. As usedherein, the term “man-portable” generally means capable of being movedreasonably easily by one person. In one embodiment, the man-portablesystem is a wheeled cart. In another embodiment, the man-portable systemis a backpack.

One embodiment of the man-portable unit includes a handheld probe,vest/backpack and two or more satchels. Other embodiments includehandheld probe, vest and backpack. The unit can be relativelyinexpensive and can be used by surgeons, doctors, dentists, scientistsand emergency personnel in the field. However, those skilled in the artwill recognize other uses for the invention. One embodiment can be usedto perform emergency cutting of a victim, removal of material, etching,marking and cauterizing of wounds. One embodiment allows the beam to cutthrough any obstacles. In one embodiment, the system can be used to gainaccess, open, cut into, or other wise free a person or object. Oneembodiment can be used to cut the top of a vehicle loose, I-beam, wood,metal, plastic, carbon fiber, cloth or fiberglass.

As illustrated in FIG. 1, in one embodiment, the man-portable system,e.g. system 100, is used in a hospital. One embodiment includes ahandheld probe, a vest and movable cart and power supplied from a wallplug. Another embodiment includes wheels on the cart. Another embodimentincludes a 120 volt or 240 Volt power supply. One embodiment, thehandheld probe, e.g. handheld probe 115, includes a beam-scanners andoptical delivery fibers. In one embodiment, the vest can include anoptical compressor, e.g. compressor 110. In another embodiment, opticalamplifiers, e.g. amplifier 105, are positioned on or in the cart. In oneembodiment, the cart includes a control module, e.g. control module 125;a control panel, e.g. control panel 130; a pulse generator, e.g. pulsegenerator 135; a power supply, e.g. power 120; a video camera, e.g.video camera 140; a video monitor, e.g. video monitor 145; an air flushsystem, e.g. air flush system 150; a suction system, e.g. suction system155; and a marker beam generator, e.g. marker beam generator 160.

The concentration of pulse energy on a small spot enables the use ofsemiconductor-optical amplifiers or moderate-power fiber-amplifiers, aswell as higher power Cr:YAG amplifiers. One embodiment includes a shortinitial optical pulse allows compression into a short pulse with anefficient and physically small compressor. Another embodiment hasmultiple semiconductor amplifiers or fiber amplifiers. In oneembodiment, the amplifiers are Cr:YAG amplifiers. In one embodiment, theamplifier has a short (e.g., 1 nanosecond or less) initial optical pulsethat undergoes controlled amplification and is then compressed into ashort (sub-picosecond) pulse, and the light pulse focused onto a smallarea, e.g., spot. In one embodiment, the area is between about 10 andabout 50 microns in diameter. In one embodiment, the spot is scannedover an area to be ablated, wherein a controllable rate of ablation isachieved. One embodiment controls the amplifiers by controlling pulsepower. One embodiment independently controls the ablation rate and pulseenergy of multiple moderate-power amplifiers. In another embodiment, theamplifier is easily cooled. Thus, by the use of a combination ofinnovations, can now provide an efficient, reasonably priced,man-portable ablation system for medical and other purposes.

One embodiment includes a laser-amplifier and compressor that allow thesystem size is reduced, whereby the system to be man-portable. In oneembodiment a semiconductor oscillator-driven pulse generator is used togenerate a pulse between about ten picoseconds and about one nanosecondwavelength-swept-with-time. In one embodiment, the initial pulse isamplified by an optically-pumped amplifier. In one embodiment, theamplifier is an erbium-doped fiber amplifier or EDFA or a Cr:YAGamplifier. In one embodiment, the pulse is compressed by an air-pathbetween gratings compressor or a Treacy grating air-grating compressor,wherein the compression creates a sub-picosecond ablation pulse. Oneembodiment has semiconductor optical amplifier (SOA) and a chirped fibercompressor, wherein the pulse is between about one to twenty nanosecond.In one embodiment, a semiconductor generates the initial pulse and a SOApreamplifier to amplify the initial pulse before introduction into theamplifier.

Different embodiments can be used for different applications dependingon the specific needs of that application. One embodiment uses anoptically-pumped—amplifier and air-grating-compressor to reduce cost,but another embodiment uses a SOA and chirped-fiber-compressor toproduce an efficient and small system.

Ablative material removal can be done either in-vivo or on the bodysurface. As some materials ablate much faster than others and materialis most efficiently removed at pulse energy densities about three timesthe materials ablation threshold. In one embodiment, the ablation rateis controlled. In one embodiment, the pulse energy density is controlledto produce a pulse energy densities about three times the materialsablation threshold. In one embodiment, the surgical ablation has athreshold of less than one Joule per square centimeter, however otherembodiments have an ablation threshold of up to about two Joules persquare centimeter.

Again, as materials ablate at different thresholds, efficient operationrequires control of the pulse energy density. One embodiment controlsthe pulse energy, thereby controlling the pulse energy density. Oneembodiment uses a fiber amplifier operating at high repetition rates.One embodiment controls the pulse energy by controlling the opticalpumping power. Another embodiment controls the pulse energy bycontrolling the pulse repetition rate. In another embodiment, the systemis fine tuned by controlling optical pumping power.

In one embodiment, the pulse energy is controlled by repetition rate andoptically pumped amplifier operating temperature is controlled throughcontrolling optical pumping power. In one embodiment, the pulse energyof semiconductor optical amplifiers (SOAs) is adjusted by changing theamplifier current. In one embodiment, the pulse energy applied to thebody is between about 2.5 and about 3.6 times the ablation threshold ofthe body portion being ablated.

In one embodiment, the ablation rate is controlled independent of pulseenergy. The use of two or more amplifiers in a train mode (pulses fromone amplifier being delayed to arrive at the spot one or morenanoseconds after those from another amplifier) allows step-wise controlof ablation rate independent of pulse energy density. Without thisdelay, the efficiency is significantly reduced. The use of train-modeamplifiers in either type of system provides faster ablation, whileproviding greater cooling surface area to minimize thermal problems. Inone embodiment, two or more amplifiers are operated in a train mode. Atlower desired ablation rates, one or more amplifiers can be shut down.In one embodiment, one or more amplifiers in train mode are shut down.

As illustrated in FIG. 2, one embodiment of the present inventionincludes a method of material removal using surgical ablative, eitherfrom an in-vivo surface or from an outside surface with a short opticalpulse that is amplified and then compressed, comprising: Step 200,generating an initial wavelength-swept-with-time pulse in a pulsegenerator within a man-portable system; Step 210, amplifying the initialpulse and then Step 220, compressing the amplified pulse within theman-portable system, wherein the amplifying and compression are donewith either an optically-pumped-amplifier and air-path between gratingscompressor combination, or a SOA and chirped fiber compressorcombination; and Step 230, applying the compressed optical pulse to thesurface.

In one embodiment, the amplifying and compressing is done with anoptically-pumped-amplifier and an air-path between gratings compressorcombination, wherein the pulses are between about ten picoseconds andabout one nanosecond. In another embodiment, the amplifying andcompressing is done with a SOA/chirped-fiber-compressor combination,wherein the initial pulses between about one and about twentynanoseconds.

Another embodiment includes a method of ablative material removal, froma surface or with a short optical pulse that is amplified and thencompressed, comprising: generating an initial pulse in a pulsegenerator; amplifying the initial pulse and then compressing theamplified pulse within the man-portable system, wherein the amplifyingis done with either an optically-pumped-amplifier or a SOA; compressingthe amplified pulse to a duration of less than one picosecond; andapplying the compressed optical pulse to the surface, wherein thegenerating, amplifying and compressing are done within a man-portablesystem. In one embodiment, two or more optically-pumped opticalamplifiers or SOA optical amplifiers are used in a train mode and thecompressed optical pulse is applied to the surface in a small area spot,wherein the spot area is between about ten and about 50 microns indiameter. In one embodiment, the pulse generator is semiconductoroscillator-driven.

In one embodiment, the amplifying and compressing is done with anoptically-pumped-amplifier and air-path between gratings compressorcombination, wherein the initial pulses are between about tenpicoseconds and about one nanosecond. In one embodiment, the fiberamplifier is an erbium-doped or erbium/ytterbium fiber amplifier and theair-path between gratings compressor is a Treacy grating compressor. Inone embodiment, two or more fiber amplifiers are used with onecompressor. In another embodiment, the amplifier is an SOA and thecompressor is a chirped optical fiber. In other embodiments, the pulseenergy density and ablation rate are independently controlled. In otherembodiments, the fiber amplifier and the amplifier temperature can beindependently controlled.

High ablative pulse repetition rates are preferred and the total pulsesper second (the total system repetition rate) from the one or more(train mode) optical amplifiers is preferably greater than 0.6 million.In one embodiment, the ablative pulse repetition rates are 0.6 millionor more.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a system implementing one embodiment of theinvention.

FIG. 2 is a flowchart illustrating the method used in one embodiment ofthe invention.

DETAILED DESCRIPTION OF THE INVENTION

While the making and using of various embodiments of the presentinvention are discussed in detail below, it should be appreciated thatthe present invention provides many applicable inventive concepts thatcan be embodied in a wide variety of specific contexts. The specificembodiments discussed herein are merely illustrative of specific ways tomake and use the invention and do not delimit the scope of theinvention.

To facilitate the understanding of this invention, a number of terms aredefined below. Terms defined herein have meanings as commonly understoodby a person of ordinary skill in the areas relevant to the presentinvention. Terms such as “a,” “an” and “the” are not intended to referto only a singular entity, but include the general class of which aspecific example may be used for illustration. The terminology herein isused to describe specific embodiments of the invention, but their usagedoes not delimit the invention, except as outlined in the claims.

Ablative material removal previously this has been done using systemswith optical benches weighing perhaps 1,000 pounds and occupying about300 cubic feet. Previous approaches have generally operatedmaximum-sized amplifiers at maximum-power and amplifyinglonger-and-longer pulses.

In one embodiment, the man-portable unit is used in a hospital andincludes a handheld probe, a vest, control-cart and receive power from awall plug. In one embodiment, the handheld probe contains beam-scannersand optical delivery fibers. In one embodiment, the vest containsoptical compressors and the optical amplifiers are positioned in thecart. In one embodiment, the cart contains the control module, thecontrol panel, the pulse generator, the power supplies, a video camera,a video monitor, air flush system, a suction system and a marker beamgenerator.

In one embodiment, the optical-fiber-containing umbilical cables areused between components. In one embodiment, the umbilical includes ahollow ablation fiber for pulses compressed to sub-picosecond duration.One embodiment, the fiber is a hollow optical fiber, a video-camerafiber, an illumination fiber, a marker-beam fiber, an air flush tube, asuction tube and wiring for the scanners.

One embodiment is battery-powered and contains a probe, vest, backpackand one or more satchels. In one embodiment, the handheld probe containsbeam-scanners and optical delivery fibers. One embodiment includes avest containing optical compressors, optical amplifiers and controldevices. In one embodiment, the control devices are control knobs,switches, buttons, dial or pad, positioned in or on the cart. In oneembodiment, the backpack contains the control module, the pulsegenerator, the power supplies, a marker beam generator, and a batterypack. In one embodiment, the satchel contains a video camera, a videomonitor, an illumination source, and additional batteries. Oneembodiment is operable without the satchel. Another embodiment includesthe video camera in the backpack and a heads-up display providing avideo monitor and a display of control settings.

In one embodiment, the handheld probe containspiezoelectrically-driven-mirror beam-scanners and optical deliveryfibers. In one embodiment, the delivery fiber has a lens on thefiber-end near the probe tip and transmits a video image back to thevideo camera. In another embodiment, a fiber illuminates the ablationregion. In another embodiment, a hollow optical fiber brings ablationpulses to the beam-scanner minors. In another embodiment, a fiber isused to bring a laser marker beam to the beam-scanner minors. In anotherembodiment, the marker beam is scanned. In one embodiment, the lasermarker beam shows the entire scan area, however other embodiments turnthe beam off and on by the specifications of area, color and distancefrom target. Another embodiment shows the area that would be ablated ifthe ablation beam were on. In other embodiments, the marker beam changescolor to indicate whether the ablation beam is on or off. In anotherembodiment, the probe contains tubes for suction and/or gas flush.

One embodiment, the man-portable units includes a handheld probe,handheld probe, vest/backpack and one or more satchels. The unit can berelatively inexpensive and can be used by surgeons, doctors, dentists,scientists and emergency personnel in the field. However, those skilledin the art will recognize other uses for the invention. In oneembodiment, the unit can be used to cut a victim and cauterize wounds.In another embodiment, the system uses microsecond long,thermally-inducing, pulses to cauterize a wound. One embodiment can beused to perform emergency cutting of a victim or an object, removal ofmaterial, etching, marking and cauterizing of wounds. One embodimentallows the beam to cut through any obstacles. In one embodiment, thesystem can be used to gain access, open, cut into, or other wise free aperson of object. One embodiment can be used to cut the top of avehicle, I-beam, wood, metal, plastic, carbon fiber, cloth orfiberglass.

One embodiment uses one or more optically-pumped amplifiers ofmoderate-power, with a short optical pulse that is amplified and thencompressed into a short pulse with the light pulse focused onto a smallarea spot. One embodiment of the present invention rapidly scans thespot over an area to be ablated and controls the pulse power to maximizeablation efficiency.

One embodiment controls the ablation rate and controls the pulse energydensity in the ablation spot. If the spot size is fixed or otherwiseknown, this can be achieved by controlling pulse energy; or if the pulseenergy is known, by controlling spot size. In one embodiment usingoptically-pumped amplifiers, the pulse energy is controlled step-wise bycontrolling repetition rate and fine-tuned by controlling opticalpumping power. In another embodiment, the pulse energy of asemiconductor optical amplifier (SOA) is adjusted by changing thecurrent thru the amplifier.

Further, it is preferred that ablation rate be controllable independentof pulse energy. One embodiment allows step wise control of the ablationrate independent of pulse energy through using two or more amplifiers inparallel a train mode (pulses from one amplifier being delayed to arriveone or more nanoseconds after those from another amplifier). Otherembodiments allow a lower ablation rates by shutting off one or moreamplifiers (e.g., the optical pumping to the fiber amplifier shut off),whereby there will be fewer pulses per train. One embodiment uses 20amplifiers producing a maximum of 20 pulses in a train, however otherembodiments use three or four amplifiers producing three or four pulsesper train.

Generally, the optical amplifiers are pumped by laser diodes operatingquasi-continually and are amplifying about 100,000 times per second forone nanosecond pulses. One embodiment uses optical amplifiers pumped bylaser diodes. Another embodiment uses non-CW-pumping in operatingamplifiers, whereby the amplifiers run in a staggered fashion, e.g., onfor a first one second period and then turned off for one second period,and a first-period-dormant amplifier turned on during the second period,and so forth, to spread the heat load.

In some embodiments, the system is man-portable and includes a wheeledcart or a backpack. As used herein, the term “man-portable” means asystem utilizing an optical amplifier that is either anoptically-pumped-amplifier or a SOA with components that can bepositioned by one man (e.g., as opposed to being mounted on a opticalbench weighing hundreds of pounds), regardless of whether the system isdesigned to be easily moved or not. One embodiment includes anoptically-pumped-amplifier with a compressor sized for a compression ofbetween about ten picoseconds and about one nanosecond, or a SOA with achirped-fiber-compressor, and which is designed to be reasonably easilymoved.

One embodiment includes a method of ablative material removal, from asurface with a short optical pulse that is amplified and thencompressed, including generating an initial pulse in a pulse generatorwithin a man-portable system; amplifying the initial pulse and thencompressing the amplified pulse within the man-portable system, whereinthe amplifying and compression are done with either a fiber-amplifierand about ten picosecond and about one 1 nanosecond pulse-compressorcombination, or a SOA and chirped fiber compressor combination; andapplying the compressed optical pulse to the surface.

In one embodiment, the amplifying and compressing is accomplished withan optically-pumped-amplifier and air-path between gratings compressorcombination. In one embodiment, the oscillator pulses are between aboutten picoseconds and about one nanosecond. In another embodiment, theamplifying and compressing is done with a chirped fiber compressorcombination. In one embodiment, the amplified pulses are between aboutone and about twenty nanoseconds in duration.

We have now found that certain laser-amplifier, compressor combinationsenable practical, and significant size reduction, which in turn enablesthe system to be man-portable. One embodiment includes a man-portablesystem capable of being moved reasonably easily by one person. In oneembodiment, the system includes a wheeled cart or possibly even beingcarried in a backpack, whereby the system is moveable from room to room.One embodiment uses initial pulses of between about ten picoseconds andabout one nanosecond, with the initial pulse amplified by anoptically-pumped-amplifier and compressed by an air-path betweengratings compressor, with the compression creating a sub-picosecondablation pulse. In one embodiment, the amplifier is an erbium-dopedfiber amplifier or EDFA amplifier. In one embodiment, the gratingcompressor is a Treacy grating compressor.

Another embodiment uses a semiconductor optical amplifier (SOA) and awith a chirped fiber compressor. One embodiment uses pulses of betweenabout one and about twenty nanoseconds during amplification. Oneembodiment uses a semiconductor generated initial pulse and a SOApreamplifier to amplify the initial pulse before introduction into thefiber amplifier.

While the compressors in either type of system can be run with inputsfrom more than one amplifier, reflections from other parallel (as usedherein, “parallel” includes train mode) amplifiers can cause a loss ofefficiency, and thus should be minimized. The loss is especiallyimportant if the amplifiers are amplifying signals at the same time, asis the case with the SOAs. In one embodiment each of the parallel SOAshas its own compressor, wherein the amplified pulses are then put into asingle fiber after the compressors, whereby reflections from the joining(e.g., in a star connector) are reduced greatly before getting back tothe amplifier. In one embodiment one or more fiber amplifiers are usedwith a single compressor, whereby the nanosecond spacing ofsub-nanosecond pulses minimizes amplifying of multiple signals at thesame time.

Fiber amplifiers have a storage lifetime of about 100 to 300microseconds and for ablations purposes; fiber amplifiers have generallyheretofore been operated with a time between pulses of almost equal toor greater than the storage lifetime, and thus are generally run a reprate of less than 3-10 kHz. Fiber amplifiers are available with averagepower of 30 W or more. One embodiment uses a moderate-power 5 W averagepower fiber amplifiers producing pulses of about 500 microJoules or moreto produce energy densities above the ablation threshold needed fornon-thermal ablation, and increasing the energy in such a system,increases the ablation rate in either depth or allows larger areas ofablation or both.

In one embodiment an optically-pumped amplifier with a time betweenpulses of a fraction of the storage lifetime is used. In one embodiment,the optically-pumped amplifier with a time between pulses of aboutone-half or less of the storage lifetime. In one embodiment, a smallerspot is scanned to produce a larger effective ablation area. In oneembodiment, the spot is about 50 microns or less in diameter. Otherembodiments produce spots of about 60 or 75 microns or more. Spot sizesherein are given as circle diameter equivalents, a “50 micron” spot hasthe area of a 50 micron diameter circle, but the spot need not be round.

One embodiment uses parallel amplifiers to generate a train of pulses toincrease the ablation rate by further increasing the effectiverepetition rate, whereby avoiding thermal problems. Another embodimentallows control of ablation rate by the use of a lesser number ofoperating fiber amplifiers. Another embodiment uses a SOA preamplifierto amplify the initial pulse before splitting to drive multiple parallelfiber amplifiers and another SOA before the introduction of the signalinto each amplifier, whereby rapid shutting down of individualamplifiers can be achieved. Other embodiments operate with pulses atabout three times the ablation threshold for greater ablationefficiency.

One embodiment uses about a 1 ns pulse with an optically-pumpedamplifier and air optical-compressor to produce compression withapproximately 40% losses. In one embodiment, the compressor is a Treacygrating compressor. At lower compressions, e.g., less than 1 nanosecond,the losses in a Treacy grating compressor are generally lower. If theother-than-compression losses are 10%, two nanoJoules are needed fromthe amplifier to get one nanoJoule on the target. One embodiment uses1550 nm light. The use of greater than one nanosecond pulses in an airoptical-compressor presents two problems; the difference in path lengthfor the extremes of long and short wavelengths needs to be more three cmand, thus, the compressor is large and expensive, and the lossesincrease with a greater degree of compression.

Another embodiment uses a semiconductor optical amplifier (SOA) and achirped fiber compressor is generally run with pulses of between aboutone and twenty nanosecond during amplification, and is operated atrepetition rates with a time between pulses of more that thesemiconductor storage lifetime. Another embodiment uses a SOApreamplifier to amplify the initial pulse before splitting to drivemultiple SOAs. One embodiment scans a small ablation spot over a largereffective ablation area. In some embodiments with SOA Amplifiers ascanned spot that is smaller than the optically-pumped amplifier spot.One embodiment uses a semiconductor generated initial pulse.

Parallel amplifiers can be used to generate a train of pulses toincrease the ablation rate by further increasing the effectiverepetition rate. Again, the pulse energy densities at operated at aboutthree times the ablation threshold. One embodiment uses two or moreamplifiers in parallel train mode, wherein pulses from one amplifierbeing delayed to arrive one or more nanoseconds after those from anotheramplifier. Other embodiments one or more amplifiers can be shut offproducing fewer pulses per train. In one embodiment twenty amplifiersare used to produce a maximum of 20 pulses in a train, however, otherembodiments use three or four amplifiers producing three or four pulsesper train. In one embodiment, CW operation is used for operatingamplifiers, wherein amplifiers might be run for e.g., one second andthen turned off and a dormant amplifier turned on to spread the heatload.

In one embodiment controls the input optical signal power, opticalpumping power of fiber amplifiers, timing of input pulses, length ofinput pulses, and timing between start of optical pumping and start ofoptical signals to control pulse power, and average degree of energystorage.

One embodiment includes an optical fibers have a maximum power of 4 MW,and thus, a 10-microJoule ablation pulse is amplified for a period asshort as two picosecond. Thus, a fiber amplifier with this type of fibercan operates with an about ten ps, about 10 microJoule pulse, at 500 kHz(or 50 microJoule with 100 kHz). However, in embodiments where heatingis a problem, multiple fiber amplifiers can be operated in a rotatingmode. One embodiment rotates the operation of ten fiber amplifiers suchthat only five were operating at any one time (e.g., each on for1/10^(th) of a second and off for 1/10^(th) of a second).

One embodiment includes ten optically-pumped amplifiers with time spacedinputs e.g., by 1 ns, to give a train of one to 10 pulses. Oneembodiment uses 5 W amplifiers operating at 100 kHz (and e.g., 50microJoules) and step between 100 kHz and 1 MHz. With 50% post-amplifieroptical efficiency and about 50 microJoules, to get about six J/sq. cmon the target, the spot size would be about 20 microns.

One embodiment includes 20 amplifiers with time spaced inputs, e.g., by1 ns, to giving a train of one to 20 pulses, 5 W amplifiers operating at50 kHz (and e.g., 100 microJoules) this can step between 50 kHz and 1MHz. With 50% post-amplifier optical efficiency and 100 microJoules, toget 6 J/sq. cm on the target, the spot size would be about 33 microns.The amplified pulse is between about 50 and about 100 picoseconds long.One embodiment includes 10 amplifiers at 50 kHz to step between 50 kHzand 500 kHz.

Generally, it is the pulse generator that controls the input repetitionrate of the amplifiers to tune energy per pulse. Another embodimentincludes 5 W amplifiers operating at 20 kHz (and e.g., 250 microJoules).With 10 amplifiers this can step between 20 kHz and 200 kHz. With 50%post-amplifier optical efficiency and 250 microJoules, to get 6 J/sq. cmon the target, the spot size would be about 50 microns. The amplifiedpulse is between 100 to 250 picoseconds long. Another embodimentincludes 30 amplifiers that steps between 20 kHz and 600 kHz.

Although very-high power SOA's can be built, they are quite expensiveand generally require large cooling systems. Therefore one embodimentuses a SOA with a lower power and a longer period of amplification, fromabout one and about twenty nanoseconds, and preferably between aboutfive and about twenty nanoseconds. Air-grating compressors areimpractically large at these time periods. Therefore one embodiment ofthe man-portable SOA amplifier systems uses chirped fiber gratings (suchgratings are commercially available from 3M). Another embodiment usesfiber amplifiers and use chirped fiber gratings, whereby these fibergratings can be shorter, with less compression than those used with ourSOAs.

Another embodiment generates a sub-picosecond pulse and time stretchingthat pulse within semiconductor pulse generator to give the initialwavelength-swept-with-time pulse.

One embodiment uses light leakage from the delivery fiber to getfeedback proportional to pulse power and/or energy for control purposes.One embodiment measures the spot size with a video camera or a linearscan. One embodiment uses an “in-vivo” type camera (see “CameraContaining Medical Tool,” U.S. Provisional Patent Application Ser. No.60/472,071 filed May 20, 2003 which is incorporated by referenceherein). One embodiment includes a handheld beam-emitting probe thatprovides its own illumination. Other embodiments include cameras usingan optical fiber in a probe to convey an image back to a remote camerabody. Another embodiment includes a vidicon-containing camera with aGRIN fiber lens. Still other embodiments use endoscope type cameras.

One embodiment scans a smaller ablation area by moving the beam withoutmoving the probe. Another embodiment scans a large area by moving thebeam over a first area, and then stepping the probe to second portion ofthe large area and then scanning the beam over the second area, and soon. One embodiment uses beam deflecting minors mounted on piezoelectricactuators to move the beam (see “Scanned Small Spot Ablation With AHigh-Rep-Rate,” U.S. Provisional Patent Application Ser. No. 60/471,972filed May 20, 2003 which is incorporated by reference herein). Oneembodiment scans the actuators over a larger region but with theablation beam only enabled to ablate portions with defined color and/orarea. One embodiment allows evaluation after a prescribed time throughpreset combination of time and, area and/or color.

Information of such a system and other information on ablation systemsare given in co-pending provisional applications listed in the followingparagraphs (which are also at least partially co-owned by, orexclusively licensed to, the owners hereof) and are hereby incorporatedby reference herein (provisional applications listed by docket No.,title and United States Provisional Patent Application Serial Number):

Docket No. ABI-1 “Laser Machining,” U.S. Provisional Patent ApplicationSer. No. 60/471,922; ABI-4 “Camera Containing Medical Tool,” U.S.Provisional Patent Application Ser. No. 60/472,071; ABI-6 “Scanned SmallSpot Ablation With A High-Rep-Rate,” U.S. Provisional Patent ApplicationSer. No. 60/471,972; and ABI-7 “Stretched Optical Pulse Amplificationand Compression,” U.S. Provisional Patent Application Ser. No.60/471,971; all filed May 20, 2003.

ABI-8 “Controlling Repetition Rate Of Fiber Amplifier,” U.S. ProvisionalPatent Application Ser. No. 60/494,102; ABI-9 “Controlling Pulse EnergyOf A Fiber Amplifier By Controlling Pump Diode Current,” U.S.Provisional Patent Application Ser. No. 60/494,275; ABI-10 “Pulse EnergyAdjustment For Changes In Ablation Spot Size,” U.S. Provisional PatentApplication Ser. No. 60/494,274; ABI-11 “Ablative Material Removal WithA Preset Removal Rate or Volume or Depth,” U.S. Provisional PatentApplication Ser. No. 60/494,273; ABI-12 “Fiber Amplifier With A TimeBetween Pulses Of A Fraction Of The Storage Lifetime,” U.S. ProvisionalPatent Application Ser. No. 60/494,272; ABI-14 “Controlling TemperatureOf A Fiber Amplifier By Controlling Pump Diode Current,” U.S.Provisional Patent Application Ser. No. 60/494,322; ABI-15 “Altering TheEmission Of An Ablation Beam for Safety or Control,” U.S. ProvisionalPatent Application Ser. No. 60/494,267; ABI-16 “Enabling Or Blocking TheEmission Of An Ablation Beam Based On Color Of Target Area,” U.S.Provisional Patent Application Ser. No. 60/494,172; ABI-17“Remotely-Controlled Ablation of Surfaces,” U.S. Provisional PatentApplication Ser. No. 60/494,276; and ABI-18 “Ablation Of A Custom ShapedArea,” U.S. Provisional Patent Application Ser. No. 60/494,180; were allfiled Aug. 11, 2003. ABI-19 “High-Power-Optical-Amplifier Using A NumberOf Spaced, Thin Slabs,” U.S. Provisional Patent Application Ser. No.60/497,404 was filed Aug. 22, 2003.

ABI-20 “Spiral-Laser On-A-Disc,” U.S. Provisional Patent ApplicationSer. No. 60/502,879 and “Laser Beam Propagation in Air,” U.S.Provisional Patent Application Ser. No. 60/502,886 were both filed onSep. 12, 2003. ABI-22 “Active Optical Compressor,” U.S. ProvisionalPatent Application Ser. No. 60/503,659 was filed Sep. 17, 2003.

ABI-24 “High Power SuperMode Laser Amplifier” U.S. Provisional PatentApplication Ser. No. 60/505,968 was filed Sep. 25, 2003; ABI-25“Semiconductor Manufacturing Using Optical Ablation,” U.S. ProvisionalPatent Application Ser. No. 60/508,136 was filed Oct. 2, 2003; ABI-26“Composite Cutting With Optical Ablation Technique,” U.S. ProvisionalPatent Application Ser. No. 60/510,855 was filed Oct. 14, 2003; andABI-27 “Material Composition Analysis Using Optical Ablation,” U.S.Provisional Patent Application Ser. No. 60/512,807 was filed Oct. 20,2003.

ABI-28 “Quasi-Continuous Current in Optical Pulse Amplifier Systems,”U.S. Provisional Patent Application Ser. No. 60/529,425 and ABI-29“Optical Pulse Stretching and Compressing,” U.S. Provisional PatentApplication Ser. No. 60/529,443, were both filed Dec. 12, 2003.

ABI-30 “Start-up Timing for Optical Ablation System,” U.S. ProvisionalPatent Application Ser. No. 60/539,026; ABI-31 “High-Frequency RingOscillator,” U.S. Provisional Patent Application Ser. No. 60/539,024;and ABI-32 “Amplifying of High Energy Laser Pulses,” U.S. ProvisionalPatent Application Ser. No. 60/539,025 were all filed Jan. 23, 2004.

ABI-33 “Semiconductor-Type Processing for Solid-State Lasers,” U.S.Provisional Patent Application Ser. No. 60/543,086, was filed Feb. 9,2004. ABI-34 “Pulse Streaming of Optically-Pumped Amplifiers,” U.S.Provisional Patent Application Ser. No. 60/546,065, was filed Feb. 18,2004. ABI-35 “Pumping of Optically-Pumped Amplifiers,” U.S. ProvisionalPatent Application Ser. No. 60/548,216 was filed Feb. 26, 2004.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims. Moreover, thescope of the present application is not intended to be limited to theparticular embodiments of the process, machine, manufacture, compositionof matter, means, methods and steps described in the specification, butonly by the claims.

1. A system comprising: a pulse generator configured for generatingpulses; a man-portable amplifier and compressor combination configuredfor amplifying the pulses and compressing the pulses, to generateamplified compressed pulses; and a handheld probe configured forapplying the amplified compressed pulses to an object in order to removematerial therefrom.